Ditto on what JD said. When I was shopping around. I sat in a Fronteir for "giggles" to see if I liked it. it felt too much like my single cab Mazda B3000 - small, cramped, and compact were the first thoughts that came to my mind.
Definately take the time to sit in, drive, and evaluate the pro's and con's of each.
Best of luck!
Also, if you are looking for a "truck" and willing to lay down the money that new ST's are costing...why not consider an F150 for a truck? You can always ask around for an X-plan pin number to help too. Just a thought.